JPH06174412A - Heated probe for scanning tunneling microscope and probe holder - Google Patents

Abstract

PURPOSE:To provide a probe capable of being heated and having a high center symmetric property and high rigidity and provide a probe holder. CONSTITUTION:A heated probe system is constituted of a probe 2 fixed to a center electrode 21, a hairpin type conducting wire 10 welded near the tip section 1 of the probe 2, and an outside electrode 22 fixing the conducting wire 10. The tip 1 of the probe 2 can be kept invariably clean, and a microscope resistant to thermal distortion and external vibration and capable of making a high-speed scan can be realized.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a scanning tunneling microscope, and more particularly to improvement of a probe portion thereof.

[0002]

2. Description of the Related Art As a conventional scanning tunneling microscope probe holder, a cylindrical holder is often used without a probe heating mechanism. However, in order to obtain a stable scanning tunneling microscope image, it is necessary to heat and clean the tip of the probe. FIG. 2 shows a conventional probe holder having a function of passing an electric current through the probe for heating. In this conventional example, it has two electrodes 20, and an electric current is passed through the hairpin type conductive wire 10 passed between the electrodes to heat the tip portion 1 of the probe.

[0003]

However, the conventional probe holder is poor in central symmetry, so that the thermal strain when the temperature of the probe holder changes due to heating of the probe or heating of the sample becomes symmetrical. As a result, there is a problem that the position of the tip of the probe is largely displaced.

In addition, since the conductive wire 10 also has a function of supporting the tip portion 1 of the probe, when the conductive wire is made thin to reduce the current value required for heating and to reduce the temperature change of the probe holder. There is also a problem in that the strength of supporting the tip portion 1 of the probe also decreases, and the vibration resistance performance and high-speed scanning performance of the probe deteriorate.

[0005]

In order to solve the above problems, in the holder of the present invention, two electrodes for passing a probe heating current are substantially concentric. Further, the cross-sectional area of all or part of the wire material fixed to one of the concentric electrodes is different from the cross-sectional area of the wire material fixed to the other.

[0006]

The operation of the present invention will be described with reference to FIG. Since the two electrodes 21 and 22 for passing the probe heating current are substantially concentric, it is easy to design concentric with the mechanism for fixing the probe holder to the probe scanning mechanism 30. Therefore, when the temperature of the probe holder changes due to the heating of the probe tip 1 or the heating of the sample, thermal deformation is caused by the probe 2
The change in the position of the probe tip 1 can be suppressed to a minimum.

Further, by threading the outer electrode 22 and fixing the probe holder to the probe scanning mechanism by this screw, a sufficiently small and rigid probe holder exchange mechanism can be constructed. At this time, the center electrode 21 is electrically connected by frictional contact.

The trade-off between the rigidity of the tip portion of the probe and the minimization of the heating current can be solved by separating the portion supporting the tip portion of the probe from the heating portion. That is, the cross-sectional areas of the hairpin type conductive wire 10 and the probe 2 may be different. At this time, the smaller cross-sectional area is in charge of heating,
The other works to support the tip of the probe. Although it depends on the materials used, in order to sufficiently separate the functions, it is preferable that the cross-sectional area ratio of the two should be 1: 2 or more. Further, it is preferable that the difference in cross-sectional area is large, but if one is too thin, handling becomes difficult and there is also a problem that the life is shortened. Therefore, the cross-sectional area ratio becomes 1: 100 or less. Is preferred.

In contrast to the method of changing the cross-sectional area of the entire wire rod, a method of reducing the cross-sectional area only in the vicinity of the tip of the probe is also effective in order to heat only the tip of the probe more efficiently.
This makes it possible to further reduce the temperature change of the probe holder. Methods for reducing the cross-sectional area of only the tip of the probe include methods such as electrolytic polishing, mechanical polishing, and welding of two types of wire rods.

[0010]

FIG. 1 shows an embodiment of the present invention. This embodiment is composed of a probe 2 fixed to a center electrode 21, a hairpin type conductive wire 10 welded near the tip 1 of the probe, and an outer electrode 22 fixing the conductive wire. Hairpin type conductive wire 10
Are fixed to the outer electrode 22 at two locations. The probe 2 and the hairpin type conductive wire 10 may be fixed by friction,
It is more desirable to use welding or screw fixing. In this embodiment, since the diameter of the hairpin type conductive wire 10 is less than half the diameter of the probe 2, the portion heated by the flow of the electric current is mainly the conductive wire 10 and the tip portion 1 of the probe is mainly used. The part supported by is the probe 2. In this embodiment, the outer electrode 22 is threaded so that the probe scanning mechanism 30 and the probe holder can be separated and connected.

FIG. 3 shows another embodiment of the present invention. In this embodiment, since the diameter of the probe 2 is less than half the diameter of the hairpin-type conductive wire 10, the portion heated by the flow of the electric current is mainly the probe 2, and the tip 1 of the probe is mainly used. The portion supporting the wire becomes the conductive wire 10.

FIG. 4 shows still another embodiment of the present invention.
In this embodiment, the diameter of the probe 2 near the probe tip 1 is smaller than the diameter near the root of the probe. The heating is concentrated in this narrowed portion, and it is possible to minimize the heating of the probe holder.

[0013]

EFFECTS OF THE INVENTION It is possible to realize a scanning tunnel microscope which can keep the tip of a probe clean at all times and is resistant to thermal strain and external vibration and capable of high-speed scanning. As a result, a stable scanning tunneling microscope image can be obtained even in a situation where the adsorption of impurities on the probe is a problem such as in a low vacuum, in a gas atmosphere, or during molecular beam irradiation.

[Brief description of drawings]

FIG. 1 is a cross-sectional view showing an embodiment of a scanning tunneling microscope heating probe holder according to the present invention.

FIG. 2 is a cross-sectional view showing a conventional scanning tunneling microscope heating probe holder.

FIG. 3 is a sectional view showing another embodiment of the scanning tunneling microscope heating probe holder according to the present invention.

FIG. 4 is a sectional view showing a scanning tunneling microscope heating probe holder according to another embodiment of the present invention.

[Explanation of symbols]

1 ... Tip of tip, 2 ... Tip, 10 ... Hairpin type conductive wire,
20 ... Electrode, 21 ... Center electrode, 22 ... Outer electrode, 30 ...
Probe scanning mechanism.

Claims (4)

[Claims] 1. A probe holder used in a scanning tunneling microscope having a mechanism for heating a probe by applying an electric current to the probe,
A scanning tunneling microscope heating probe holder, wherein the two electrodes for passing the current are substantially concentric. 2. A probe of a scanning tunneling microscope mounted on the probe holder according to claim 1, wherein a cross-sectional area of a wire fixed to one of said concentric electrodes is a cross section of a wire fixed to the other. A scanning tunneling microscope heating probe characterized by having a different area. 3. A probe for a scanning tunneling microscope mounted on the probe holder according to claim 1, wherein the probe tip of one of the two wire rods fixed to the concentric electrode. A scanning tunneling microscope heating probe, wherein the cross-sectional area near the portion is smaller than the cross-sectional area of the portion fixing the wire to the electrode. 4. The scanning tunneling microscope heating probe according to claim 2, wherein the wire rods having different cross-sectional areas have a cross-sectional area ratio of 1: 2 or more and 1: 100 or less.